A conventional vacuum cleaner (cleaning robot), which is an autonomous traveling type, for example, cleans a floor surface as a surface to be cleaned, while traveling on the floor surface autonomously and detecting an obstacle etc. by using a sensor, vacuum cleaner is generally controlled in such a way that after it finishes cleaning, the vacuum cleaner returns to a charging unit (goes home) autonomously for charge of a built-in secondary cell. The charging unit outputs a guide signal such as an infrared ray to guide the vacuum cleaner to the charging unit.
For example, to guide the vacuum cleaner, the charging unit outputs a left-side guide signal and a right-side guide signal. The vacuum cleaner is controlled to move to the right side relatively in response to receipt of the left-side guide signal and to the left side relatively in response to receipt of the right-side guide signal. As a result, the vacuum cleaner can be guided towards the charging unit along an area where both of these guide signals can be received.
If the charging unit is to output these left-side and right-side guide signals simultaneously, these signals should be of different types so as to be distinguished from each other. This complicates a structure or processing required for generating signals. Additionally, the charging unit is to output guide signals all the time. As a result of this, a large amount of power will be consumed and interference with a signal output, for example, from a different unit may be caused easily.